1. Field of the Invention
The invention relates to a spine folded portion flattening apparatus for flattening the curved spine folded portion of a folded sheet bundle, and particularly flattening the spine folded portion while moving the sheet bundle, a sheet treating apparatus and an image forming apparatus provided with the same.
2. Related Background Art
Heretofore, a predetermined number of sheets, e.g. about 20 or fewer sheets have been stacked one upon another and have been folded into the form of a pamphlet by a suture/folding machine. As the sheet bundle folded by such a suture/folding machine, there is a simply folded sheet bundle, a saddle-stitched and folded sheet bundle, a sheet bundle not bound by yarn or staple but bound by an adhesive (perfect binding) and folded, or the like.
However, any of these sheet bundles has more or less elastic force and therefore, after it has been folded, the periphery of a spine folded portion (a top of the folded portion or a spine) bulges out into a U-shape, and the open side or the so-called fore edge of the folded sheet bundle has tended to open. Such sheet bundles, when piled, assume an unstable state, and has been liable to get out of shape and difficult to keep storing in a piled state or transport.
Against such a problem, there is a spine folded portion flattening apparatus for flattening the spine folded portion of a folded sheet bundle so that the folded sheet bundle can be placed flatly (see Japanese Patent Application Laid-Open No. 2001-260564).
The conventional spine folded portion flattening apparatus is shown in FIGS. 13, 14, 15A, 15B and 15C of the accompanying drawings. The spine folded portion flattening apparatus 101 first receives, by a vertically movable stop plate 105, a pamphlet-shaped twice-folded saddle-stitched sheet bundle S discharged in the direction indicated by the arrow B from a pair of folding rollers 107 with the spine folded portion (spine) Sb thereof as a leading edge and stops it (FIG. 15A). Thereafter, the spine folded portion flattening apparatus 101 grips the sheet bundle by grip members 102 and 103, and elevates the stop plate 105 to a waiting position (FIG. 15B). At this time, the spine folded portion Sb protrudes from the grip members 102 and 103. The stop plate 105 separates from the spine folded portion Sb. Then, the spine folded portion flattening apparatus 101 urges a pressure contact roller 104 against the spine folded portion Sb and moves it in the direction indicated by the arrow A (see FIG. 13) along the spine folded portion Sb. The spine folded portion Sb so far curved is pressed by the pressure contact roller 104 and becomes flat. Lastly, the spine folded portion flattening apparatus 101 discharges the flattened sheet bundle S onto a sheet discharging tray 108 in the direction indicated by the arrow B by a pair of discharge belt 106 and stacks it thereon (FIG. 15C). As described above, the conventional spine folded portion flattening apparatus 101 has stopped the sheet bundle and flattened the spine folded portion of the sheet bundle by the pressure contact roller 104.
Also, the conventional spine folded portion flattening apparatus 101, as shown in FIG. 16 of the accompanying drawings, has sometimes been incorporated in a sheet treating apparatus 120. The sheet treating apparatus 120 is connected to the apparatus main body 122 of an image forming apparatus 121, and cooperates with the apparatus main body 122 to constitute the image forming apparatus 121. The image forming apparatus 121 is adapted to form an image on a sheet.
The sheet treating apparatus 120 is provided with a sheet folding apparatus 109 for making sheets into a bundle shape and folding the bundle, a stapler 170 for binding the bundle-shaped sheets, a fixed sheet tray 123 and a stack tray 114 serving as vertically movable stacking means. The sheet tray 123 is adapted to stack thereon sheets discharged from the apparatus main body 122 without being subjected to any treatment. The stack tray 114 is adapted to stack thereon sheet bundles bound into a bundle shape by the stapler 170. The stack tray 114 is adapted to be moved down in conformity with the thickness of the whole of the stacked sheet bundles.
The conventional spine folded portion flattening apparatus 101 incorporated in the sheet treating apparatus 120 of the image forming apparatus 121 has been adapted to discharge a sheet bundle having had its spine folded portion flattened in a direction (the direction indicated by the arrow B in FIGS. 13 and 15C) in which it has been fed into the spine folded portion flattening apparatus 101. A sheet discharge tray portion 108 for receiving the discharged sheet bundle has been disposed beneath the stack tray 114.
The conventional spine folded portion flattening apparatus 101, however, has stopped the sheet bundle S and flattened the spine folded portion Sb of the sheet bundle S by the pressure contact roller 104 and therefore, had to stop the conveyance of the sheet bundle S as long as the pressure contact roller 104 was moved along the longitudinal direction of the spine folded portion Sb. Therefore, the conventional spine folded portion flattening apparatus 101 has been poor in the efficiency of the spine folded portion flattening process correspondingly to the time for which the conveyance of the sheet bundle S is stopped.
Also, the conventional sheet treating apparatus is provided with the spine folded portion flattening apparatus poor in the process efficiency as described above and therefore, under the influence of the process efficiency of the spine folded portion flattening apparatus, it has been poor in the sheet treating efficiency as the entire sheet treating apparatus.
Further, the conventional image forming apparatus is provided with the spine folded portion flattening apparatus which is poor in the process efficiency of flattening the spine folded portion and therefore, under the influence of the process efficiency of the spine folded portion flattening apparatus, it has been poor in the image forming efficiency as the entire image forming apparatus.